Smart electronic switch for low-power loads

A two-wire electronic switch adapted to be coupled between an AC power source and an electrical load for turning the electrical load on and off, the electronic switch comprising:

• a controllably conductive device adapted to be coupled in series electrical connection between the source and the load, the controllably conductive device adapted to conduct a load current through the load when the controllably conductive device is conductive;
• a controller operatively coupled to the controllably conductive device for controlling the controllably conductive device to be conductive and non conductive to turn the load on and off, respectively;
• an output capacitor operable to develop a DC supply voltage for powering the controller;
• and
• an in-line power supply coupled in series with the controllably conductive device, the in-line power supply further coupled to the output capacitor for controlling when the output capacitor charges in order to generate the DC supply voltage across the output capacitor when the controllably conductive device is conductive, such that the output capacitor stops charging when the magnitude of the DC supply voltage reaches a maximum DC supply voltage threshold, a voltage developed across the in-line power supply when the output capacitor is charging having a substantially small magnitude as compared to a peak voltage of an AC line voltage of the AC power source, the output capacitor adapted to conduct the load current for at least a portion of a line cycle of the AC power source when the controllably conductive device is conductive;
• wherein the in-line power supply controls when the output capacitor charges asynchronously with respect to the frequency of the AC power source, such that the output capacitor is operable to start and stop charging at any time during each half cycle, the power supply operable to start and to stop charging the output capacitor at least once during each half cycle of the AC power source;
• and
• wherein the controller is operable to determine when the magnitude of the DC supply voltage reaches the maximum DC supply voltage threshold, and to render the controllably conductive device non-conductive immediately after the DC supply voltage reaches the maximum DC supply voltage threshold.